I had an issue with my Keurig B44 whereby the pump would turn on but it would not draw any water up into the heating reservoir. First thing I checked was the mesh filter inside the holding tank which was fine, I then checked the pump which turned out to be pumping water normally. Next I removed the top cover and found my issue to be the one way check valve was gummed up. I removed this valve and cleaned it out with some hot water and the issue was resolved. Hopefully this can help somebody else out who may have the similar issue.